The present invention relates to a thermal-type over load relay having a contact operating mechanism, and particularly to an improvement of such a contact operating mechanism.
Hitherto, a thermal-type over load relay has been used for the purpose of protecting a three-phase induction motor from burning out due to overload. There have been known thermal-type over load relays of a type having a contact operating mechanism composed of a normally closed contact, a normally open contact, and an operating rod for operating the normally open contact. However, such a contact operating mechanism is bulky in size and it is not possible to manually test its operation easily. Moreover, malfuntions of the contacts due to externally applied mechanical shocks frequent.